As a variable valve lift device having an engine valve lift amount change mechanism, there is a device shown in the following Patent Document 1. The variable valve lift device shown in the following Patent Document 1 is composed of, as shown in FIGS. 1 to 4 of the following Patent Document 1, an input shaft (cam shaft) 100, a valve opening/closing unit (rocker arm mechanism) 200 which has a rocker arm receiving pressing force by an input cam 110 and bias force in a valve closing direction by a biasing means (not shown), and a connecting portion (a lift amount change mechanism) which changes a lift amount of an engine valve.
A lift arm 440 receives pressing force from the rotating input cam. 110 via a connecting link 430 coupled by a roller 413, a second member 412, and a first connecting pin 450. As a result, the lift arm 440 rotates around an eccentric shaft 300, that rotates a needle bearing 220 of the rocker arm in contact with a lift arm contact portion 441 having a free-form surface shape. As a result, due to the needle bearing 220 rotating while being in contact with a predetermined range of the lift arm contact portion 441, the valve opening/closing unit 200 causes the engine valve to perform an opening/closing operation in a lift amount based on the free-form surface shape of the contact range of the lift arm contact portion 441.
On the other hand, in the case where a lift amount of the valve is changed, the eccentric shaft 300 is rotated, to move the first connecting pin 450 coupled to a control shaft 420. At that time, a position in contact with the input cam 110 is changed on the roller 413, and a contact range between the lift arm contact portion 441 and the needle bearing 220 of the rocker arm is changed on the lift arm 440. As a result, in the valve opening/closing unit 200, a shape of the free-form surface of the lift arm contact portion 441 is changed in the range in contact with the needle bearing 220, and therefore, a lift amount of the engine valve is changed.